Technical Abstract:
Microsatellite or simple sequence repeats (SSRs) are tandem 1-6 bases repeated motifs, found in coding and noncoding regions of prokaryotic and eukaryotic genomes. Due to the high nucleotide substitution rate in noncoding regions, SSRs exhibit a high degree of molecular polymorphism. SSRs markers are a powerful genetic tool in plant genetics and breeding. Our lab has developed nearly 1000 SSR markers in flowering dogwood and kousa dogwood, and these markers have been applied to identifying inter- and intra- specific hybrids with these two species; identification of cultivars of the two Cornus species, and genomic mapping of C. florida. Two flowering dogwood SSR loci were used to identify six hybrids from two crosses between flowering and kousa dogwood. Five kousa dogwood SSR loci were used to verify 181 kousa dogwood intra-specific hybrids and two flowering dogwood SSR loci were used to verify four flowering dogwood intra-specific hybrids. A dichotomous key was developed for flowering and kousa dogwoods using SSR markers. Four SSR loci separated 22 flowering dogwood cultivars and lines. In kousa dogwood, five SSR loci were used to identify 22 cultivars. The information provided in the two dichotomous keys will be useful for parental and hybrid verification and plant patent issues in flowering and kousa dogwood. Lastly, a total of 224 SSR loci were applied to an F2 population of 94 individuals from a cross between two flowering dogwood cultivars, ‘Appalachian Spring’ × ‘Cherokee Brave’, from which 289 clear genetic markers were found. These 289 markers are being used to generate 11 linkage groups for flowering dogwood. The data is currently being processed and the first linkage map in flowering dogwood is expected to be completed by the end of 2008.